My point about out in the sun was that the closed bag will warm up the pot and help the reaction along and also vent the nasties outside. As it happens, I put my pot out yesterday afternoon. I had planned to remove the handle and screw from the lid but I forgot until a few minutes ago when I saw your post. I was afraid that the handle and screw might be damaged, so I took the lid out of the sunning bag and washed it off. I could see that some internal crud was oozing down the pot, so cleaning was happening. Upon lid examination, the black crud (much less than your bottom) came right off with an easy rub with a green scrub sponge. The handle and screw didn't seem to be damaged. Some dingy crud on the bumpy white inner surface came off with more scrubbing. I plan to leave the pot out for another day. From this, I would expect that your black crud will come off completely and easily. I hope that we will have success with the more critical inner surfaces. Time will tell. Mine is a small 7 inch pot. The inner surface appeared scorched or cracked. I was only using it to bake the no knead breads and the surface was of no concern. I got it for $7 at a thrift store. If it turns out just to be crud that can be removed, I will have a nice deal. Otherwise we will have learned more about cleaning them. Good luck.

My Kohler Whitehaven does not always look dirty but I have the grills and make an effort not to let food - especially fruit scraps - sit in the sink. This is much easier now that I don't have a bunch of little ones to watch after - though husband still drops tea bags in the sink - usually right after I cleaned it:) As cast iron sinks get older they get micro abrasions in the finish and stain more easily, but it is very easily cleaned. I will use the same philosophy of those with white cabinets - I can see when cleaning needs to happen. My previous cast iron sink was 20 years old. Almost every night I would give it a spritz of clorox and it would whiten right up. I do't need to clean my Whitehaven that often - maybe twice a week, but as time goes on it may need cleaning more often, but then its a sink and should be cleaned regularly.

I have the Rohl Allia you posted above. Before that, I had a Rohl Allia double bowl in my previous home. I have had the current sink for over 6years. No crazing at all. There is one chip from dropping a drill in it but you can barely see the chip and it has never bothered me. I have a sink grid that I purchased about three years ago. I can do with or without a grid. I love the location of the drain in this sink and agree with others that a drain in the center is not always preferred. I also have a Waterstone faucet. I posted in the thread linked about. Although the faucet is made in the US, it is made of parts from all over the world. I had a Grohe Ladylux before and loved it. I also like my Waterstone faucet but would not pay more than the Grohe for it. Good luck!

I don't know who said nobody in the US refinishes cast iron these days, but that's not true. There are folks out there who do it, but they are few and far between (usually hard to find on Google because they're small businesses), and usually expensive. I'm pretty sure there is one in/near Richmond, VA because I was looking into purchasing a vintage claw foot tub at one time and remember coming across a company that restored the vintage cast iron tubs (this was in 2016/2017 timeframe). I also once saw a DIY refinishing kit online. If you can't find anyone nearby to reglaze it for you, and you're out of other options, maybe the DIY kit would be worth a try. I think it's really hard work though, so something like the Rust-Oleum Tub & Tile kit would be last ditch effort... though I'd probably learn to love the stains before trying to "paint" it.